Sintered oilless bearing and motor using the same

Abstract

A sintered oilless bearing and a capstan motor using the same includes first and second bearings inserted into an inside surface of a bearing holder and spaced-apart from each other within the bearing holder, and non-porous and porous parts formed on corresponding ones of the first and second bearings. The non-porous parts have an angle between 91° and 120° with respect to a center line of the first and second bearings, are disposed to face each other, or are disposed between the porous parts to compensate for a position deviation of the non-porous parts of the first and second bearings occurring due to an assembling dispersion between the first and second bearings, to maintain a lubrication property and a stable oil film. The non-porous parts and the porous parts of the first and second bearings have different pore ratio, and the first and second bearings are formed by sintering a bronze series compound.

What is claimed is:  
     
         1 . A sintered oilless bearing having an inside surface, comprising: 
 a single non-porous part; and    a single porous part,    wherein the single non-porous part and the porous part are formed on the inside surface, a pore ratio of the non-porous part is less than 10% according to a formula (the pore ratio=a sum of pore surface areas of a portion/a surface area of the portion), the pore ration of the porous part is between 40% and 60% inclusive, the porous part is formed on the inside surface other than the non-porous part, and the sintered oilless bearing is made of a bronze series compound which is sintered at a sinter temperature.    
     
     
         2 . The bearing of  claim 1 , wherein the non-porous part has a width corresponding to an angle between 91° and 120° inclusive with respect to a longitudinal center axis of the sintered oilless bearing.  
     
     
         3 . The bearing of  claim 1 , wherein the non-porous part has a width corresponding to an angle of 100° with respect to a longitudinal center axis of the sintered oilless bearing.  
     
     
         4 . The bearing of  claim 1 , wherein the bronze series compound comprises: 
 a mixture having a copper powder and a tin powder with a ratio of 90-97% of copper to 3-10% of tin.    
     
     
         5 . The bearing of  claim 1 , wherein the bronze series compound comprises: 
 a mixture having copper and tin powders having a particle size between 300 mesh and 350 mesh at a ratio of 50 weight % of a total weight of respective ones of the copper and tin powders.    
     
     
         6 . The bearing of  claim 1 , wherein the bronze series compound has the sinter temperature between 720° C. and 760° C. inclusive.  
     
     
         7 . A sintered oilless bearing having an inside surface, comprising: 
 a plurality of non-porous parts; and    a plurality of porous parts, wherein the non-porous parts and the porous parts are alternatively formed on the inside surface, a pore ratio of the non-porous part is less than 10% according to a formula (the pore ratio=a sum of pore surface areas of a portion/a surface area of the portion), the pore ratio of the porous part is between 40% and 60% inclusive, the porous part is formed on the inside surface other than the non-porous part, and the sintered oilless bearing is made of a bronze series compound which is sintered at a sinter temperature.    
     
     
         8 . The bearing of  claim 7 , wherein each non-porous part has a width corresponding to an angle between 91° and 120° inclusive with respect to a longitudinal center axis of the sintered oilless bearing.  
     
     
         9 . The bearing of  claim 7 , wherein the bronze series compound comprises: 
 a mixture having a copper powder and a tin powder with a ratio of 90-97% of copper to 3-10% of tin.    
     
     
         10 . The bearing of  claim 7 , wherein the bronze series compound comprises: 
 a mixture having copper and tin powders having a particle size between 300 mesh and 350 mesh at a ratio of 50 weight % of a total weight of respective ones of the copper and tin powders.    
     
     
         11 . The bearing of  claim 1 , wherein the bronze series compound has the sinter temperature between 720° C. and 760° C. inclusive.  
     
     
         12 . The bearing of  claim 1 , wherein each non-porous part has a width corresponding to an angle of 100° with respect to a longitudinal center axis of the sintered oilless bearing, and the non-porous parts are disposed on two portions of the inside surface at an interval of 180°.  
     
     
         13 . The bearing of  claim 1 , wherein each non-porous part has a width corresponding to an angle of 100° with respect to a longitudinal center axis of the sintered oilless bearing, and the porous parts are disposed on a remaining portion of the inside surface on which the non-porous parts are not formed.  
     
     
         14 . A capstan motor comprising: 
 a rotor case having a shaft having a first end coupled to the rotor case and a second end extended from the first end, having a surface on which a magnet is mounted, and having an open end;    a base plate covering the open end, and having a bearing holder through which the second end of the shaft passes;    a stator coil mounted on the base plate to generate a magnetic force with the magnet;    a first bearing inserted into a first portion of the bearing holder, having a first inside surface with a first single non-porous part and a first single porous part, and having a pore ratio of the first non-porous part is less than 10% according to a formula (the pore ratio=a sum of pore surface areas of a portion/a surface area of the portion), the pore ratio of the first porous part being between 40% and 60% inclusive, the first porous part formed on the first inside surface other than the first non-porous part, and the sintered oilless bearing made of a bronze series compound which is sintered at a sinter temperature; and    a second bearing inserted into a second portion of the bearing holder, having a second inside surface with a second single non-porous part and a second single porous part, and having a pore ratio of the second non-porous part less than 10% according to the formula (the pore ratio=a sum of pore surface areas of a portion/a surface area of the portion), the pore ratio of the second porous part being between 40% and 60% inclusive, the second porous part formed on the second inside surface other than the second non-porous part, and the sintered oilless bearing made of the bronze series compound which is sintered at the sinter temperature.    
     
     
         15 . The bearing of  claim 14 , wherein each of the first and second non-porous parts has a width corresponding to an angle between 91° and 120° inclusive with respect to a longitudinal center axis of the sintered oilless bearing.  
     
     
         16 . The bearing of  claim 14 , wherein each of the first and second non-porous parts has a width corresponding to an angle of 100° with respect to a longitudinal center axis of the sintered oilless bearing.  
     
     
         17 . The bearing of  claim 14 , wherein the bronze series compound comprises: 
 a mixture having a copper powder and a tin powder with a ratio of 90-97% of copper to 3-10% of tin.    
     
     
         18 . The bearing of  claim 14 , wherein the bronze series compound comprises: 
 a mixture having copper and tin powders having a particle size between 300 mesh and 350 mesh at a ratio of 50 weight % of a total weight of respective ones of the copper and tin powders.    
     
     
         19 . The bearing of  claim 14 , wherein the bronze series compound has the sinter temperature between 720° C. and 760° C. inclusive.  
     
     
         20 . A capstan motor comprising: 
 a rotor case having a shaft having a first end coupled to the rotor case and a second end extended from the first end, having a surface on which a magnet is mounted, and having an open end;    a base plate covering the open end, and having a bearing holder through which the second end of the shaft passes;    a stator coil mounted on the base plate to generate a magnetic force with the magnet;    a first bearing inserted into a first portion of the bearing holder, having a first inside surface with a plurality of first non-porous parts and a plurality of first porous parts which are formed to be arranged alternatively around the first inside surface, and having pore ratio of the first non-porous parts less than 10% according to a formula (the pore ratio=a sum of pore surface areas of a portion/a surface area of the portion), the pore ratio of the first porous parts is between 40% and 60% inclusive, the first porous parts formed on the first inside surface other than the first non-porous parts, and the sintered oilless bearing made of a bronze series compound which is sintered at a sinter temperature; and    a second bearing inserted into a second portion of the bearing holder, having a second inside surface with a plurality of second non-porous parts and a plurality of second porous parts which are formed to be arranged alternatively around the second inside surface, and having a pore ratio of the second non-porous parts less than 10% according to the formula (the pore ratio=a sum of pore surface areas of a portion/a surface area of the portion), the pore ratio of the second porous parts between 40% and 60% inclusive, the second porous parts formed on the second inside surface other than the second non-porous part, and the sintered oilless bearing made of the bronze series compound which is sintered at the sinter temperature.    
     
     
         21 . The bearing of  claim 20 , wherein each of the first and second non-porous parts has a width corresponding to an angle between 91° and 120° inclusive with respect to a longitudinal center axis of the sintered oilless bearing.  
     
     
         22 . The bearing of  claim 20 , wherein the bronze series compound comprises: 
 a mixture having a copper powder and a tin powder with a ratio of 90-97% of copper to 3-10% of tin.    
     
     
         23 . The bearing of  claim 20 , wherein the bronze series compound comprises: 
 a mixture having copper and tin powders having a particle size between 300 mesh and 350 mesh at a ratio of 50 weight % of a total weight of respective ones of the copper and tin powders.    
     
     
         24 . The bearing of  claim 20 , wherein the bronze series compound has the-sinter temperature between 720° C. and 760° C. inclusive.  
     
     
         25 . The bearing of  claim 20 , wherein each of the first and second non-porous parts has a width corresponding to an angle of 100° with respect to a longitudinal center axis of the sintered oilless bearing, and the first and second-porous parts are disposed on two portions of corresponding ones of the first and second inside surfaces at an interval of 180°.  
     
     
         26 . The bearing of  claim 20 , wherein each of the first and second non-porous parts has a width corresponding to an angle of 100° with respect to a longitudinal center axis of the sintered oilless bearing, and the first and second porous parts are disposed on a remaining portion of corresponding ones of the first and second inside surfaces on which corresponding ones of the first and second non-porous parts are not formed.